• 한국유체기계학회 논문집
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• 제13권3호
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• pp.37-42
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• 2010

This study investigated on details of flow characteristics of a multi-blade fan for domestic ventilation. Experiments and analysis were carried out to describe on flow pattern with variations of cut-off angle near the scroll housing throat, which were performed by PIV measurement for the flow field and by total pressure probes. The stagnation point at cut-off region of the fan moves to the exit of the scroll housing as the cut-off angle increases. The movement of stagnation point and the variation of throat area of the scroll housing influence to the distribution of velocity magnitude at the exit of the fan. Furthermore, a large distortion of the velocity distribution at the scroll exit causes to increase mixing loss along the flow path.

• Journal of Mechanical Science and Technology
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• 제18권1호
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• pp.114-121
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• 2004

In order to investigate the corrosion fatigue characteristics in the weld of multi-pass welded A 106 Gr B steel pipe, corrosion fatigue tests were performed under the various stress ratios and 3.5 wt% NaCl solution at room temperature. The corrosion fatigue characteristic curves were represented using crack closure concept. The obtained results are as follows : when the load frequency is 1.0 Hz, the crack opening point is transited in the region of $K_{max}$=20∼32 MPaㆍ $m^{1}$2/. In the low stress intensity factor range, the crack opening point is higher than that in air. However, in the high stress intensity factor range, it is lower than that in air. In the cases of 0.1 Hz and 0.01 Hz, the crack opening point gradually decreases to $K_{min}$ with $K_{max}$ increase.rease.

• 반도체디스플레이기술학회지
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• 제8권1호
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• pp.43-48
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• 2009

We have examined the problem of the number of quad-tree blocks that an n-dimensional rectangle will be decomposed into on the average. the contribution of this paper are both practical and theoretical. In this paper, we develops the overlapping multi-scale models and the region quad-tree models which is useful in computer graphics animation, image processing, pattern recognition and also for modeling three dimensional objects. These models, which represent something of a conceptual departure from other models developed for multi-scale framework were developed with the specific interest of producing smooth estimates.

• 소성∙가공
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• 제24권3호
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• pp.187-193
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• 2015

The objective of the current study is to determine cross-sectional profile of intermediate dies in order to improve the plastic strain homogeneity which directly affects not only the dimensional accuracy but also the mechanical properties of final product by redesigning the intermediate dies using the conventional electric field analysis (EFA) method. Initially, the multi-pass shape wire drawing was designed by using the equivalent potential lines from EFA. The area reduction ratio was calculated from the number of passes in multi-pass shape wire drawing but constrained by the capacity of the drawing machine and the drawing force. In order to compensate for a concentration of strain in a region of the cross section of the wire, the process for multi pass wire drawing from initial round material to an intermediate die was redesigned again using the electric field analysis. Both drawing process designs were simulated by the finite element method in which the strain distribution and standard deviation plastic strain of the cross section of drawn wires were examined.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권1호
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• pp.452-472
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• 2019

Most existing wavelet-based multiplicative watermarking methods are affected by geometric attacks to a certain extent. A serious limitation of wavelet-based multiplicative watermarking is its sensitivity to rotation, scaling, and translation. In this study, we propose an image watermarking method by using dual-tree complex wavelet transform with a multi-objective optimization approach. We embed the watermark information into an image region with a high entropy value via a multiplicative strategy. The major contribution of this work is that the trade-off between imperceptibility and robustness is simply solved by using the multi-objective optimization approach, which applies the watermark error probability and an image quality metric to establish a multi-objective optimization function. In this manner, the optimal embedding factor obtained by solving the multi-objective function effectively controls watermark strength. For watermark decoding, we adopt a maximum likelihood decision criterion. Finally, we evaluate the performance of the proposed method by conducting simulations on benchmark test images. Experiment results demonstrate the imperceptibility of the proposed method and its robustness against various attacks, including additive white Gaussian noise, JPEG compression, scaling, rotation, and combined attacks.

• 제어로봇시스템학회논문지
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• 제13권11호
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• pp.1074-1081
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• 2007

This paper presents a method for real-time face detection and tracking which combined Adaboost and Camshift algorithm. Adaboost algorithm is a method which selects an important feature called weak classifier among many possible image features by tuning weight of each feature from learning candidates. Even though excellent performance extracting the object, computing time of the algorithm is very high with window size of multi-scale to search image region. So direct application of the method is not easy for real-time tasks such as multi-task OS, robot, and mobile environment. But CAMshift method is an improvement of Mean-shift algorithm for the video streaming environment and track the interesting object at high speed based on hue value of the target region. The detection efficiency of the method is not good for environment of dynamic illumination. We propose a combined method of Adaboost and CAMshift to improve the computing speed with good face detection performance. The method was proved for real image sequences including single and more faces.

• 한국의류학회지
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• 제36권7호
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• pp.778-789
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• 2012

The characteristics of ancient gagye (the cubic hair style which added wigs or other materials to hair) that appeared in mural paintings were compared between Pyongyang and Jian in Goguryeo and the midlands, the northwest region, and the northeast region in China for the same period (Han to Weijin, and Northern and Southern Dynasties). Gagye in Korea and China was classified into circle type, hat type, high-bun type, and multi-bun type; in addition, Han elements, northern race elements, Goguryeo elements, and uniqueness were compared and analyzed according to regional distribution, trend periods, and style characteristics. The Han elements of ancient gagye in Korea and China appeared in the hat type, the high-bun type, and accessories that left the hair down. The northern race elements were found in the circle type and multi-bun type. The uniqueness of Goguryeo elements included a circle from the circle type, a triangle style from the hat type, an up-do style from the high burn type, and simplified hair accessories.

• 전기전자학회논문지
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• 제25권4호
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• pp.650-663
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• 2021

Subsurface topology estimation is an important factor in the geophysical survey. Electrical impedance tomography is one of the popular methods used for subsurface imaging. The EIT inverse problem is highly nonlinear and ill-posed; therefore, reconstructed conductivity distribution suffers from low spatial resolution. The subsurface region can be approximated as piece-wise separate regions with constant conductivity in each region; therefore, the conductivity estimation problem is transformed to estimate the shape and location of the layer boundary interface. Each layer interface boundary is treated as an open boundary that is described using front points. The subsurface domain contains multi-layers with very complex configurations, and, in such situations, conventional methods such as the modified Newton Raphson method fail to provide the desired solution. Therefore, in this work, we have implemented a 7-layer artificial neural network (ANN) as an inverse problem algorithm to estimate the front points that describe the multi-layer interface boundaries. An ANN model consisting of input, output, and five fully connected hidden layers are trained for interlayer boundary reconstruction using training data that consists of pairs of voltage measurements of the subsurface domain with three-layer configuration and the corresponding front points of interface boundaries. The results from the proposed ANN model are compared with the gravitational search algorithm (GSA) for interlayer boundary estimation, and the results show that ANN is successful in estimating the layer boundaries with good accuracy.

• 소성∙가공
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• 제32권5호
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• pp.268-275
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• 2023

ISO 21029 cryogenic vessel is used to transport cryogenic fluids. High-manganese steel (High-Mn steel) is widely regarded as suitable for use at cryogenic temperatures. The conventional way of manufacturing an ellipsoidal vessel head involves incremental stretching, followed by a spinning process. In this study, an alternative method for forming an ellipsoidal vessel head was proposed. Finite element analysis (FEA) was used to theoretically examine the strain evolution during a multi-stage forming process, which involved progressive stretching, deep drawing, and spinning of High-Mn steel. The distribution of effective strain and strain components were analyzed at different regions of the formed part. The FEA results revealed that only normal strains were evident in the dished region of the vessel head due to the stretching process. However, the flange region experienced complex strain evolution during the subsequent deep drawing and spinning process.

• 한국항만경제학회지
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• 제26권1호
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• pp.259-276
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• 2010

본 연구에서는 국제적인 공항과 항만을 동시에 지닌 인천의 복합운송시스템 구축을 위한 역할과 과제는 무엇인지 살펴보기 위해 물류기업 및 공공기관, 연구기관 임직원을 대상으로 개별 심층면접조사(Depth Interview)를 실시하여 국제복합운송 물류거점 선점을 위한 경쟁력 요인선정, 주요 도시별 복합운송측면에서의 경쟁력 점수를 측정하였다. 주요 도시별 경쟁력 최종 점수를 100점 만점으로 환산하여 살펴보면 1위는 상해(64.8점), 2위 홍콩(64.5점), 3위 인천(62.9점), 4위 부산(60.4점) 등으로 나타나 인천이 향후 동북아지역에서 국제복합운송 물류거점으로서 발전할 수 있는 잠재력은 어느 정도 보유한 것으로 평가되었다. 또한 본 연구 분석 결과를 토대로 인천지역이 동북아 지역의 복합운송거점으로서의 나아가야 할 발전방안에 대해서 제시하면 첫째, 인천-천진간 해공복합운송 공동물류센터 건립 및 제도 간소화 협정체결사업이 필요하며, 둘째, 인천-상해간 해륙복합운송활성화를 위한 페리-트럭 복합운송 활성화를 위한 선박에서 통관절차 수행 등의 제도 개선 추진사업이 요구된다.